It is well known that electroforming may be utilized for preparing a die or mold which cannot readily be machined by cutting and other mechanical processes. In this process a layer of metal is electrodeposited on a shaped mold from a solution containing the metal by passing an electric current between the mold poled cathodic and an anode spaced therefrom through the solution, and the metal layer or electroform progressively built up on the mold is subsequently removed therefrom to form a desired article.
Conventional approaches to the electroforming of shaped articles are, however, laborious, time-consuming and expensive and have much to be desired.
A major problem is that the removal of an electroform from the receiving mold particularly is difficult because the former as required conforms intimately to the latter. The difficulty increases as the form complexity or depth increases. The removal may be achieved by dissolving the mold. This measure has been found impractical, however, where the form is intricate since it is difficult then to leave the electroform intact. Moreover, the mold becomes useless. It is quite often desirable that one shaped mold be serviceable for repeated use or for reuse on a purposeful modification. It is thus indeed essential that both the electroform and the forming mold upon separation or physically pulling one off the other be left intact. To facilitate the separation, it is known to mirror-finish the surface of a mold prior to the electroforming process and to paint the mirror-finished mold surface with a lubricating agent such as an iodide or a sulfide. Not only are these measures laborious and time-consuming but they are often unsatisfactory or insufficient to significantly reduce the pulling force required to remove the electroform from the mold. Furthermore, extreme care and skill are required not only in the finishing and painting stages in order to maintain the integrity of the mold surface but in the pulling stage in order not to damage the electroform or the mold, especially again where the form is intricate in shape, or where it is deep and has a large area of surfaces which extend substantially in parallel to the direction in which the pulling force is applied to achieve the removal. A slight mishandling may deform the electroform or cause defects therein. It should also be mentioned that the painting is even detrimental to the subsequent electroforming process results in substantial loss in efficiency and therefore in increased costs.
Another disadvantage inherent to the conventional art of preparing a shaped article from an electroforming mold resides in the slowness, complexity and inefficiency of the electroforming process itself. When a layer of metal is to be electroformed on a mold which is more or less intricate, dendrite or like crystalline formations tend to build up on certain localized areas thereon. In order to reduce these build-ups the electroforming process is carried out at a minimum current density so that it may take several days for the electroformed metal layer to reach a required thickness of 0.5 to 5 mm. However, these undesired formations cannot completely be eliminated even in the low-current density process. It has thus been necessary and the common practice to interrupt the electroforming process from time to time so that the metal layer either on or off the mold is removed from the electroforming machine and transferred to a cutting plant for machining to remove these formations. After each such corrective stage, it is necessary that the metal layer be fully degreased, washed, cleaned, and then returned to the electroforming machine. Since the timing of the need for such removal is generally difficult to predict, the electroforming process must be constantly monitored or otherwise interrupted for nights. Furthermore, the frequency of the interruptions needs to be increased as the electroforming current density is increased which not only accelerates the forming rate but the rate of dendrite build-up and hence the frequency of the need for corrective machining. It is thus apparent that not only is the conventional electroforming process labor-, time- and energy-consuming but it wastes chemicals and other useful resources.
Severe problems in the art also exist in the stages of preparing electroforming molds and their transfer. According to the existing practice, an electroforming mold has been produced by a separate manufacture or at a distant site remote from the electroforming concern so that considerable time, labor and expenditure are again necessary for the transportation. Furthermore, one given electroforming mold is seldom produced in multiples while some of a similar specification may be needed at intervals.